This application claims the priority of Korean Patent Application No. 10-2004-0012536, filed on Feb. 25, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of exposing using an electron beam.
2. Description of the Related Art
Along with the development of a technology of manufacturing a semiconductor device, an equipment for manufacturing a semiconductor device is also improved. An example of the equipment for manufacturing a semiconductor device is an equipment for exposing using an electron beam. Nowadays, equipments of adopting various methods of exposing are introduced to improve productivity.
Examples of the introduced equipments include an equipment for changing the spot size of electron beams during an exposure, a projection type equipment, and an equipment to which an optical system of multi-electron beam type, multi-column type, and optical lithography type is adopted.
In an equipment for exposing using an electron beam, primary electrons, secondary electrons, and photons, in other words, an x-ray, are detected when the electron beam is injected into a specimen or a photosensitive layer. In addition, the electrons are scattered when the electron beam is injected into the specimen or the photosensitive layer. Here, such scattered electrons become obstacles when realizing fine patterns.
The electron scattering can be divided into two types like a forward scattering, which is generated in a photosensitive layer in the incidence direction of the electron beam, and a backward scattering, which is generated from a substrate.
The forward scattering affects the distribution of the electron beams in the photosensitive layer. Thus, when performing an exposure by using the electron beam, the photosensitive layer is mainly affected by the forward scattering than the backward scattering. Accordingly, the effective width of the electron beam is increased at a lower portion of the photosensitive layer.
The effect of the electron scattering is severe when patterns are adjacent.
For example, when the patterns to be exposed are adjacent, the electron beam exposure for one pattern affects the other pattern, which is located in an electron scattering area. In other words, the electron beam is injected to an area of the photosensitive layer where the electron beam is not to be injected, thus the pattern is distorted.
Such phenomenon is referred to as a proximity effect that can be divided into two types like an intra-proximity effect, which is generated within the same pattern, and an inter-proximity effect, which affects adjacent patterns.
The electron scattering also increases the temperatures of the inside and the surface of the photosensitive layer. When the temperatures of the inside and the surface of the photosensitive layer are increased, the exposing characteristic of the photosensitive layer is changed, thus, the pattern is distorted.
In the exposure by using the electron beam, an exposing area of the specimen or the photosensitive layer is divided into main fields, and the main fields are divided into a plurality of sub-fields. The main field denotes a maximum deflection area of the specimen or the photosensitive layer that may be exposed by scanning the electron beam once while a chuck is fixed. The sub-field denotes a numerical area of a pattern corresponding to 1 bit, when the minimum amount of signal information transferred by the equipment for exposing using the electron beam at once is 1 bit.
In a conventional method of exposing using an electron beam shown in FIG. 1, first through fourth main fields MF1, MF2, MF3, and MF4 defined in an exposing area 10 are exposed sequentially. In addition, sub-fields SF of each main field are sequentially exposed. For example, when exposing the first main field MF1, a first sub-field SF1 is exposed, a second sub-field SF2 is exposed, and a third sub-field SF3 is exposed. The exposure is performed until the last sub-field SFn is exposed. Arrows shown in the first main field MF1 denote the direction of progress of the exposure using the electron beam.
Since the sub-fields of the main field are sequentially exposed in the conventional method of exposure using the electron beam, the temperatures of the inside and the surface of the photosensitive layer are increased due to the electron scattering during the exposure of the sub-fields. As a result, the exposing characteristic of the photosensitive layer is changed, thus the pattern may be distorted. In other words, the numerical accuracy and precision of the pattern are deteriorated.
On the other hand, a software program for compensating the proximity effect is developed; however, the program compensates the minimum area of the proximity effect. In addition, the software program only compensates the size of the exposure pattern, and it is required to process a large amount of data to calculate a process shift amount for a portion deviated from the size of the exposure pattern. Furthermore, the software program cannot remove the proximity effect from a complicated pattern and an entire area of the pattern.